Lighting bulb



FIG. 1 is a front perspective view of a lighting bulb;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof

FIG. 5 is a right side view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a top view thereof.

CLAIM The ornamental design for a lighting bulb, as shown and described.